Abstract

The aim of this study was to investigate the degradation of an azo dye, reactive red 198 (RR198), by ozone, H2O2/O-3, H2O2/ultrasonic and combination of O-3/H2O2/ultrasonic from aqueous solutions. The effects of ozone, hydrogen peroxide doses, initial dye concentration, ultrasonic power and solution pH were studied on the degradation of RR198. The concentration of RR 198 was determined by UV-visible spectrophotometer (DR 5000 Hach) at its maximum absorption wavelength of 518 nm. The measurement of chemical oxygen demand (COD) carried out with a standard potassium dichromate oxidation method. The results showed that the degradation rate was increased by increasing H2O2 concentration. The optimum H2O2 concentration was obtained in the range of 0.03 mM at dye concentration of 200 mg/L. Alkaline pH, and 125 W ultrasonic power were favored in the color and COD removal. Moreover, compared with ozone and peroxone, the O-3/H2O2/ultrasonic process could achieve a higher color and COD removal at the same reaction time. Pseudo-first order kinetics with respect to dyestuffs concentrations was found to fit all the experimental data. H2O2/ultrasonic process has negligible effect on removal of COD compare to other process (>5). Ultrasonic was ineffective in activation of H2O2 for degradation of RR198. These findings show that oxidation by O-3/H2O2/ultrasonic is a promising alternative for the treatment of RR198 containing solution as a recalcitrant pollutant.